Research On Predictive Tracking Control Technology Of Large Telescope Based On Permanent Magnet Synchronous Motor

The telescope system is a comprehensive remote observation device that plays an important role in astronomical observation,space communication,space target monitoring and other fields.The aperture of the telescope directly determines its remote observation capability.As the aperture of the telescope continues to increase,the load carried by the drive motor of the servo system also increases.On the one hand,the direct drive method has been widely used in large telescopes in recent years,owing to its advantages such as high stiffness and no gear clearance.On the other hand,the larger aperture telescope system requires the drive motor to provide greater torque to drive the telescope load rotation.Compared with DC brushed motors,AC permanent magnet synchronous motors(PMSM)have become the best candidate for telescope direct drive motors,owing to their higher torque-inertia ratio,stronger reliability,and excellent low-speed performance.In recent years,many large telescope systems that have been built or are planned to be built abroad have chosen the direct drive method by PMSMs.However,there are relatively few domestic studies on large telescope systems direct-drived by PMSM,and the research on the related technologies is relatively incomplete.Therefore,it has great significance in engineering to develop the telescope systems which direct drived by PMSMs,and to make in-depth research on the key technologies and related control strategies of the telescope servo system.This article will be based on a ground-based optoelectronic telescope at the Changchun Institute of Optics,Chinese Academy of Sciences,and will study the control system of a PMSM.Some advanced composite control strategies such as predictive control are developed to ensure the telescope servo system to attain a better dynamic response performance and ensure the tracking accuracy,and improve the robustness and the anti-disturbance capability of the system at the same time.Thus,some ideas which will provide some ideas and relevant engineering experience for the design and development of large telescope servo control system are proposed.The research work of this article starts from the following aspects:First,the hardware design of the drive device for the PMSM control system is completed.The embedded implementation of the drive algorithm of the PMSM based on the vector control strategy is completed with this device.This device provide a hardware platform for the engineering project.The frequency test of the telescope azimuth axis turntable system is carried out by the sinusoidal frequency sweep method,and the frequency characteristic curve of the system is obtained.On the other hand,in order to obtain the control model of the system,the mechanical parameter identification method based on a sliding mode parameter observer is developed.It is used to identify the main mechanical parameter of the telescope azimuth axis turntable system — the rotational inertia.The identification result can be used in the predictive controller designed in this article.Some improvements in the process of designing the sliding mode observer can make the adjustment of design parameters easy.Then,the low-pass filtering characteristics of the sliding mode observer are analyzed,the influence of observer gain parameters on observation output is analyzed.The designed observer is very conducive to adjustment online in a practical system,and can achieve a good observation effect.In order to improve the dynamic response performance and robustness of the system,a robust tracking control method based on generalized prediction and sliding mode compensation is proposed.The method uses generalized predictive control(GPC)strategy to improve the system dynamic response performance.To overcome the influence of unmodeled disturbances such as model mismatch and parameter perturbation on the control effect,a sliding mode control compensation structure is introduced.This method can suppress the effects caused by system disturbances such as model mismatch and parameter perturbation without damaging the original performance of the predictive controller.The method ideas and implementation processes of each loop controller of a PMSM control system based on the GPC method are introduced in detail.This paper summarizes various disturbances that may be encountered during the implementation of predictive control in a telescope system.The impact of various disturbances on the traditional GPC method is analyzed.To overcome the influence of various disturbances on the control performance of the system,an anti-disturbance composite control method based on predictive control and observer compensation is proposed.A speed prediction tracking controller based on High-order terminal sliding mode observer(HTSMO)and a position prediction tracking controller based on Extended State Observer(ESO)are designed.By designing a composite control structure in which the disturbance observer is parallel to the predictive controller,this method can realize online estimation and feed-forward compensation of the system disturbance to suppress the adverse effects of the system disturbance on the control effect.This composite control strategy will enable the system to attain greatly improved the anti-disturbance ability and robustness,while keeping the good dynamic performance of the original predictive controller,and improve the tracking accuracy of the system finally.Simulation and experiment prove the effectiveness of this strategy.Compared with the traditional PI control method,the tracking error RMS value of the 0.01°/s position ramp signal and sinusoidal signal is reduced by 46.2% and 30.4%,respectively.Theoretical analysis and experiments results show that the proposed tracking control strategy of PMSM based on robust generalized predictive control algorithm and observer compensation not only has the advantages of simple design,easy implementation,and convenient adjustment,but also makes the controlled system have faster dynamic performance and stronger anti-disturbance ability.Thus,the control performance of the system has been comprehensively improved.